Systems and methods of post-processing features for additive fabrication

ABSTRACT

According to some aspects, a method of additive fabrication wherein a plurality of layers of material are formed on a build platform is provided. The method comprises forming a raft structure in contact with the build platform, the raft structure formed from one or more layers of material and comprising at least one removal pocket adjacent to the build platform and forming additional material in contact with the raft structure. According to some aspects, an additive fabrication apparatus configured to form a plurality of layers of material on a build platform is provided. The apparatus comprises the build platform, and at least one controller configured to form a raft structure in contact with the build platform, the raft structure formed from one or more layers of material and comprising at least one removal pocket adjacent to the build platform, and form additional material in contact with the raft structure.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation under 35 U.S.C. § 120 of U.S.patent application Ser. No. 14/501,967, filed Sep. 30, 2014, whichclaims the benefit of U.S. Provisional Patent Application No.61/907,446, filed Nov. 22, 2013 and U.S. Provisional Patent ApplicationNo. 62/039,615, filed Aug. 20, 2014, which are hereby incorporated byreference in their entireties.

FIELD OF INVENTION

The present invention relates generally to systems and methods foradditive fabrication (e.g., 3-dimensional printing) that form structuresto assist in post-processing of an associated fabricated part.

BACKGROUND

Additive fabrication, e.g., 3-dimensional (3D) printing, providestechniques for fabricating objects, typically by causing portions of abuilding material to solidify at specific locations. Additivefabrication techniques may include stereolithography, selective or fuseddeposition modeling, direct composite manufacturing, laminated objectmanufacturing, selective phase area deposition, multi-phase jetsolidification, ballistic particle manufacturing, particle deposition,laser sintering or combinations thereof. Many additive fabricationtechniques build parts by forming successive layers, which are typicallycross-sections of the desired object. Typically each layer is formedsuch that it adheres to either a previously formed layer or a substrateupon which the object is built.

In one approach to additive fabrication, known as stereolithography,solid objects are created by successively forming thin layers of acurable polymer resin, typically first onto a substrate and then one ontop of another. Exposure to actinic radiation cures a thin layer ofliquid resin, which causes it to harden and adhere to previously curedlayers or the bottom surface of the build platform. Subsequent tofabrication of an object, one or more post-processing steps may beperformed to clean, further cure and/or strip unwanted material from theobject.

SUMMARY

Systems and methods for additive fabrication that form structures toassist in post-processing of an associated fabricated part are provided.

Some embodiments include a method of additive fabrication wherein aplurality of layers of material are formed on a build platform,comprising forming a raft structure in contact with the build platform,the raft structure formed from one or more layers of material andcomprising at least one removal pocket adjacent to the build platform,and forming additional material in contact with the raft structure.

Some embodiments provide an additive fabrication apparatus configured toform a plurality of layers of material on a build platform, comprisingthe build platform, and at least one controller configured to form araft structure in contact with the build platform, the raft structureformed from one or more layers of material and comprising at least oneremoval pocket adjacent to the build platform, and form additionalmaterial in contact with the raft structure.

Some embodiments provide at least one non-transitory computer readablemedium comprising an executable program that, when executed, causes acomputer to perform a method of obtaining a representation of athree-dimensional object, and generating a representation of a part, thepart including a raft structure and the three-dimensional object incontact with one another at a base of the three-dimensional object,wherein the raft structure comprises at least one removal pocket.

The foregoing summary is provided by way of illustration and is notintended to be limiting.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1 illustrates an illustrative additive fabrication process in whicha part is formed that includes a raft structure, according to someembodiments;

FIG. 2 depicts a raft structure having removal pockets which, accordingto some embodiments;

FIGS. 3A-C depict an illustrative pocket structure, according to someembodiments;

FIG. 4 depicts an alternate pocket structure of a raft, according tosome embodiments;

FIGS. 5A-B depict parts formed on a build structure including raftstructures having removal pockets, according to some embodiments;

FIG. 6 depicts a method of forming a raft structure including a removalpocket, according to some embodiments;

FIGS. 7A-B depict an illustrative grip structure attached to a body of apart having a spherical shape, according to some embodiments;

FIGS. 8A-B depict another illustrative grip structure formed forinsertion into a channel, according to some embodiments;

FIG. 9 depicts an illustrative grip structure that includes features tofacilitate rotational movement around the grip structure, according tosome embodiments;

FIG. 10 depicts an illustrative grip structure that includesinformation-carrier features and a registration mark, according to someembodiments; and

FIG. 11 illustrates an example of a suitable computing systemenvironment on which aspects of the invention may be implemented.

DETAILED DESCRIPTION

Systems and methods for additive fabrication that form structures toassist in post-processing of an associated fabricated part are provided.As discussed above, in additive fabrication a plurality of layers ofmaterial may be formed on a build platform. Typically, a first layer ofthe material is formed on a build surface as an initial step of theformation process. The first layer typically provides both stability forsubsequent formation of additional layers and provides a layer throughwhich the part being formed may be adhered to the build surface. Thedegree to which the first layer and the build surface adhere to oneanother may depend on multiple factors, such as the material used toform the layer and the geometries of the build platform and/or the firstlayer. In some cases, the first layer of the part being fabricated mayhave an area that is sufficiently small that the adhesive forces betweenthe first layer and the build surface during fabrication may beinsufficient to retain contact between the part and build surface, whichmay lead to the part separating partially or completely from the buildsurface. Assuming the part successfully adheres to the build surfacethroughout the fabrication process, it is removed from the build surfaceas a post-processing step subsequent to fabrication of the part beingcompleted.

In addition to removal of a part from a build surface, post-processingmay include further steps performed subsequent to fabrication of thepart. In some use cases, material may have been formed to supportoverhanging or otherwise unsupported structures of the part, and thisexcess material may be removed (e.g., using a knife or other cuttingtool). In some use cases, cleaning of a part may be performed afterfabrication. For example, when using a photopolymer-based additivefabrication device it may be beneficial to immerse a newly formed partinto a cleaning solution such as isopropyl alcohol to remove excessuncured or partially cured resin from surfaces of the newly formed part.When using a powder-based additive fabrication technology,post-processing may include the removal and/or potential recovery ofpowder media used to form the part that has not been fused or otherwiseincorporated into the final part formed using said powder. In some usecases, the surface of a fabricated part may be altered or finished usingtechniques that etch or otherwise affect the surface characteristics ofthe part. For example, parts fabricated using a fused filament additivefabrication technology may be finished using a vapor polishing technique(e.g., using acetone vapor) which causes the surface of the part to besmoothed and appear glossy. In some use cases, a part may be immersed inwater and/or an acid/alkaline solution (e.g., sodium hydroxide) todissolve a portion of the part.

Performance of any post-processing steps, however, including but notlimited to those discussed above, may risk damage to the fabricatedpart. In many cases, fabricated parts are fragile and/or includefeatures that may be damaged or removed by certain post-processingsteps. For example, a user holding a part to perform removal of asupport structure or to perform cleaning of the part may exertsufficient force when holding the part that the force causes the part tobe damaged. In addition, a post-processing step in which a part isremoved from a build surface may cause damage to the part via the forcesthat are necessarily exerted on the part in order to remove it. In someextreme cases, the use of a scraping or cutting tool to remove a partfrom a build surface may result in injury to a user. For example, if theadhesive forces between a fabricated part an a build surface aresufficiently high, the user may have to exert considerable force inorder to separate the part from the build surface, which increases therisk of injury.

The inventors have recognized and appreciated that one or more auxiliarystructures may be formed with a fabricated part that may be shaped toassist a user in performing one or more post-processing steps of thepart. Such post-processing steps may include, but are not limited to,those described above. The auxiliary structures may, in someembodiments, be formed so as to be easily removable from the part suchthat the structures may be utilized during post-processing steps thenremoved from the body of the part (i.e., a portion of the fabricatedpart other than the auxiliary structure(s) that represents the desiredstructure).

According to some embodiments, it may be beneficial to increase thestability and/or adhesion of a fabricated part to a build surface byforming a structure, known as a “raft,” on the build surface (e.g.,prior to forming the first layer of the body of the part). By removingthe raft structure from the part after the fabrication process iscompleted, the additional stability and/or adhesion may be providedduring fabrication without impacting the form of the fabricated object.Raft structures may increase adhesion between one or more layers ofmaterial and a build surface in multiple ways, such as by increasing thesurface area in contact with the build surface.

According to some embodiments, a raft structure is formed that includesone or more “removal pockets” that aid a user in separating the raftstructure from the build surface. As indicated above, while a raftstructure may increase adhesion between a fabricated part and a buildsurface, increased adhesion may also increase the force needed toseparate the fabricated part from the build surface. Pocket structureswithin the raft structure may be shaped to allow lifting and/or peelingforces to more easily cause separation of the raft structure from thebuild platform. For example, suitable pocket structures may be shaped toallow insertion of a removal tool, which may pry or otherwise separatethe raft from the build surface using a lower force than would benecessary without the pocket structure. A suitable raft structure mayinclude any number of removal pockets, which may include any number ofdifferent shaped pocket structures.

According to some embodiments, a raft structure may include any numberof layers of material formed by an additive fabrication device, and aremoval pocket may also be formed from any number of those layers. Insome use cases, portion of the raft and/or removal pocket may be formedin layers in which portions of the body of the fabricated part are alsoformed. For example, if the raft structure includes a flat portion and araised portion, the flat portion may be formed prior to forming anyportion of the body of the part, but some or all of the raised portionmay be formed in layers in which some or all of the body is also formed.

According to some embodiments, a representation of a raft structureincluding removal pockets may be generated by computationally combininga representation of a raft with a representation of a pocket structure.The representation of the raft structure may include any number ofpocket structures as a result of the combining. For example, a polygonalrepresentation of a pocket structure may be combined with a polygonalrepresentation of a flat raft structure (e.g., via a Boolean algorithm),resulting in a polygonal representation of a raft structure having oneor more removal pockets with a shape described by the polygonalrepresentation of the pocket structure. A representation of a raftstructure may be generated from any number of such combinations, whichmay include multiple representation of removal pockets (e.g., havingdifferent shapes).

According to some embodiments, a raft structure may include one or morevoid spaces, which are regions in which no material is formed. Suitablevoid spaces may be located between at least one portion of the raftstructure and the build surface. For example, a void space mayfacilitate insertion of a tool into the void space and thereby allow forseparation of the raft structure form the build surface using the tool.According to some embodiments, a raft structure may include one or moresacrificial structures. A sacrificial structure may be formed tostrengthen or increase adhesion of a pocket structure while also tendingto collapse or easily break or fracture under forces applied to orthrough the removal pocket during the removal process. In someembodiments, at least one removal pocket comprises such a sacrificialstructure, such as within a suitable void space.

According to some embodiments, one or more removal pockets may beselected and/or placed automatically (e.g., using a suitable algorithm).The choice of pocket design structure(s) used in a raft structure, inaddition to their dimension(s), orientation(s), number and/orplacement(s) may be determined via any suitable technique or techniques.In some use cases, one or more of the above factors may be determinedbased at least in part on the geometry of the body of the part beingfabricated, one or more characteristics of the build platform on whichthe part is fabricated, forces expected to be applied through points onthe raft structure (e.g., calculated or heuristically determined), orcombinations thereof. According to some embodiments, one or more removalpockets may be selected and/or placed within a raft structure based atleast in part on manual input from a user. For example, a user interfacethat displays a representation of the raft structure may receive input(e.g., via mouse, keyboard, etc.) that dictates, at least in part, whereone or more removal pockets are to be placed.

According to some embodiments, the design of any pockets, e.g., choiceof pocket design structure(s) used in a raft structure, in addition totheir dimension(s), orientation(s), number and/or placement(s), etc. maybe based at least in part on the surface area of the associated raftstructure. In cases where a raft structure contacts a build surface overa surface area that is less than a target surface area, for example, thenumber and/or size of pockets may be chosen so as not to reduce thesurface area that is in contact below a certain threshold. Additionally,or alternatively, the design of any pockets may be chosen so as tominimally impact the surface area where a raft structure contacts abuild surface, such as by reducing the effective mechanical strength ofthe pocket(s) to reflect the lower level of expected removal forces. Inother cases where a raft structure contacts a build surface over asurface area that is greater than a target surface area, the design ofany pockets may be chosen so as to aid in removal of the raft (e.g., byincluding a larger number of pockets). The design of any such pocketsmay be alternatively or additionally modified, including by increasingthe strength of a pocket to reflect the higher level of expected removalforces.

As discussed above, some post-processing steps may result in damage to afabricated part due to forces exerted on the part during the step(s)(e.g., due to holding, mounting, shaking, etc.). According to someembodiments, an auxiliary structure that provides a “grip” may befabricated with the body of a part. The grip may allow for easier andmore effective post-processing by allowing a user to hold the gripstructure during one or more post-processing steps. Forces exerted bygripping or holding the fabricated part may thereby be applied solely orlargely to the grip structure rather than the body of the part. In someuse cases, the grip structure may be removed subsequent to performanceof any post-processing steps.

A grip structure fabricated so as to be in contact with the body of apart being fabricated may have any suitable shape and orientation andmay be attached to the body of the part at any suitable location.According to some embodiments, a grip structure includes a hook shape orincludes another shape suitable for being suspended from anotherstructure. For example, a grip structure may include a shape having aT-shaped cross-section suitable for being suspended from parallel rails.

According to some embodiments, a grip structure may be formed to includeinformation, such as information about the fabricated part. In some usecases, the grips structure includes one or more information carrierfeatures, such as digits, holes or other patterns chosen to conveyinformation. Any suitable aspects of such information-carrier features,including aspects such as location, size, and/or depth of holes, may beused to encode information. In some use cases, the grip structureincludes a registration mark.

According to some embodiments, a grip structure may be structured to beheld during immersion of the body of the part in a solution. Asdiscussed above, post-processing steps may include immersion in asolution to clean, further cure and/or to dissolve regions of the part.A grip structure may allow a user to perform the fluid immersionpost-processing step while no region of the body of the part is touchedor otherwise handled, by holding (e.g., by hand, using a tool) the gripof the part and performing the immersion.

According to some embodiments, the orientation and/or position of a gripstructure may be chosen based on an anticipated orientation of the partduring one or more post-processing steps performed while holding orotherwise handling or mounting the part via the grip structure. Forexample, a grip structure may be positioned and/or oriented on the bodyof a part so as to orient the body of the part in a particular directionwhen held or otherwise handled by the grip. Moreover, as discussedabove, a part may be suspended by a grip structure during one or morepost-processing steps. As a result, the orientation of the suspendedpart during the post-processing step may depend, at least in part, onthe location of the grip structure, and thus the suspension point. Inparticular, the position and orientation of a freely suspended part maybe substantially determined by an interaction between the suspensionpoint and the center of mass of the part, while the position andorientation of a rigidly suspended part may depend primarily on thelocation and orientation of the connection between the grip structureand a support fixture. Accordingly, the orientation and/or position ofthe grip structure may be based at least in part on the anticipatedorientation of the suspended part.

According to some embodiments, a grip structure may be oriented and/orpositioned at a location based on the orientation of the part during theformation process. As one non-limiting example, a user and/or processmay select an orientation of a part for various reasons, including togenerate support structures. Following such an orientation, a gripstructure may be added to the part based on the selected orientation,such as at a position maximally distant from the build platform giventhe selected orientation.

According to some embodiments, it may be advantageous to reorient and/ormove a part during one or more post-processing steps. In the case ofpost processing by exposure to liquids, for example, it may beadvantageous in some embodiments to immerse and remove a part on aparticular schedule of exposures. Advantages from such motions mayinclude agitation of liquid and appropriate exposure time of the part.Similarly, other post processing techniques, such as post processingwith actinic radiation, may also benefit from reorienting and/or movingthe part during one or more post-processing steps. Advantages from suchmotion may include ensuring optimal actinic radiation exposure tomultiple surfaces of the part. In some embodiments, grip features of apart may be used to simplify such reorientations and/or motions. Inparticular, automated or semi-automated fixtures such as lifting armsmay be attached to grip features irrespective of the underlying geometryof the part. In some embodiments, grip structures may be particularlydesigned for specific fixtures or devices to be used during the postprocessing. As discussed below in relation to FIG. 9, some embodimentsof the present invention may add features such as slots, or otherasymmetries, to advantageously allow for rotational forces to be moreeasily applied to the part such that the part may be more easily rotatedduring one or more post-processing steps.

According to some embodiments, a grip structure may be oriented and/orpositioned so as to avoid areas of the part with high detail and/orprominent visual or functional significance, so as to reduce the amountof post-processing needed following the removal of the grip structure.According to some embodiments, a grip structure may be oriented and/orpositioned to avoid weaker areas of the part, such as areas with thinwalls or isolated extensions, to avoid internal stresses, distortions,or failure of the part during post processing.

According to some embodiments, aspects of a grip structure (e.g., shape,size, position and/or orientation) may be determined with a minimum ofuser input in order to increase the ease of use of an additivefabrication system and decrease the risk of user error. In someembodiments, the user may select desired locations, grip shape choices,and other details to be used in the addition of the grip structure to apart. In some embodiments, automated processes may identify, select,and/or propose locations, grip shape choices, and/or other details to beused in the addition of the grip structures to a part. In someembodiments, grip creation parameters, including the optimal placementof grip structures, may depend at least in part on expectedpost-processing steps to be used and the particular post-processing stepfor which optimization is desired.

According to some embodiments, a representation of a part may begenerated by combining a representation of a grip structure with arepresentation of the body of a part. As one non-limiting example, suchcombination may be performed by generating and/or loading a geometricalmodel of the grip structure in any one of a number of appropriateformats, including voxel, NURBS surfaces, triangulated meshes, and/orother representations. The geometrical model of the grip structure maythen be scaled or otherwise modified as appropriate for the size of thepart, mass of the part, expected forces during post processing, expectedstrength of the grip, and/or as desired by the user. The geometricalmodel of the grip structure may then be combined with a geometricalmodel of the body of the part at the desired location by insertion orcombination of the geometrical model of the grip into the geometricalmodel of the desired part. Such an insertion or combination may beaccomplished in any suitable way including, but not limited to, Booleanunion operations between the geometrical model of the part and thegeometrical model of a grip structure based on voxel, mesh, and/or otherrepresentations of the respective model.

According to some embodiments, a grip structure may be optimized forimmersion within a liquid. Such immersions may include one or more timedperiods in or out of the liquid, replacement and/or circulation of theliquid, and/or agitation of the liquid and/or the part. In some usecases, movement of the part itself, such as relatively rapid insertionand removal of the part from the liquid, may provide substantial mixingand circulation within the liquid. In some embodiments, parametersregarding the grip structures (e.g., shape, size, position and/ororientation) may be optimized to account for fluid flow properties ofthe immersion liquid. As one example, a grip structure may be located soas to orient the part to avoid the creation of trapped volumes duringimmersion in a liquid and/or during subsequent removal. Such trappedvolumes may, for example, take the form of air unable to be displacedfrom internal and/or external regions of the part by post-processingliquid. Such trapped volumes may additionally or alternatively take theform of post-processing liquid unable to escape from internal and/orexternal regions of the part. In some use cases, the degree to whichtrapped volumes on the internal and/or external surfaces of a part maybe reduced or eliminated by choosing a suitable the orientation of thepart when suspended in the liquid. Such orientations may be determinedbased on user input and/or appropriate heuristic analysis of thegeometry of the part. As one example, various candidate orientations maybe generated and the flow of fluids simulated in each candidateorientation using any suitable fluid simulation technique(s). Based onsuch simulations, an orientation may be chosen which exhibits desiredfluid flow properties. Such a process may also be further integrated bytesting variations on a preferred orientation to find a locally optimalorientation.

According to some embodiments, post processing of a part may includeplacing the part within a chamber or within an enclosed environment.Such chambers are typically of a fixed size which may or may notcorrespond to the maximum size of the build environment of a relatedadditive fabrication device. As such, in some use cases, a partfabricated using the additive fabrication device may only fit withinsuch a post-processing chamber in particular orientations. Accordingly,a grip structure may be located so as to orient the output of theadditive fabrication device within the bounds of the post-processingchamber. As one example, the location of a grip structure may be chosenso as to orient the part in a substantially horizontal direction so asto fit within a post-processing chamber wherein the longest extent ofthe chamber is substantially horizontal.

According to some embodiments, post processing of a part may includeexposing the part to actinic radiation. Actinic radiation may beprojected onto the part from a number of sources and thus from a numberof directions. As such, certain portions of a part may receive more orless incident actinic radiation depending upon the orientation of thepart and the positions of the radiation sources during the exposure. Insome embodiments, a grip structure may be located so as to orient thepart to receive an optimal exposure to actinic radiation. For example,an optimal exposure may be a maximization of total actinic radiationenergy incident on the part, or may be a maximization of total actinicradiation energy on preferred portions of the part, such as on one ormore identified structures and/or on one or more detailed features ofthe part.

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, systems and methods for additivefabrication that form structures to assist in post-processing of anassociated fabricated part. It should be appreciated that variousaspects described herein may be implemented in any of numerous ways.Examples of specific implementations are provided herein forillustrative purposes only. In addition, the various aspects describedin the embodiments below may be used alone or in any combination, andare not limited to the combinations explicitly described herein.

Although the embodiments herein are primarily disclosed with respect tothe Form 1 3D Printer sold by Formlabs, Inc., the Assignee of thepresent application, and with respect to stereolithography, thetechniques described herein may be equally applicable to other systems.In some embodiments, structures fabricated via one or more additivefabrication techniques as described herein may be formed from, or maycomprise, a plurality of layers. For example, layer-based additivefabrication techniques may fabricate an object by forming a series oflayers, which may be detectable through observation of the object, andsuch layers may be any size, including any thickness between 10 micronsand 500 microns. In some use cases, a layer-based additive fabricationtechnique may fabricate an object that includes layers of differentthickness.

Although particular systems and methods for additive fabrication thatform structures to assist in post-processing of an associated fabricatedpart have been described and shown herein, it is envisioned that thefunctionality of the various methods, systems, apparatus, objects, andcomputer readable media disclosed herein may be applied to any now knownor hereafter devised additive fabrication technique wherein it isdesired to reduce the risk of damage to a fabricated part during anynumber of steps performed after fabrication.

As discussed above, the inventors have recognized and appreciated thatone or more auxiliary structures may be formed with a fabricated partthat may be shaped to assist a user in performing one or morepost-processing steps of the part. As further discussed above, asuitable auxiliary structure may include a raft structure. FIG. 1illustrates an illustrative additive fabrication process in which a partis formed that includes a raft structure. Exemplary stereolithographicprinter 100 forms a part 12 in a downward facing direction on buildplatform 4. In the example of FIG. 1, build platform 4 opposes the floorof container 6, which is filled with a photopolymer resin 10. A part 12may be formed layerwise, with an initial layer attached to the buildplatform 4.

The floor of container 6 may be transparent to actinic radiation, whichmay be targeted at portions of a layer of liquid photocurable resinresting on the floor of the container. Exposure to actinic radiationcures a thin layer of the liquid resin, which causes it to harden toform layer 14. The layer 14 is at least partially in contact with both apreviously formed layer and the surface of the container 6 when it isformed. The top side of a cured resin layer typically bonds to eitherthe bottom surface of the build platform 4 or, in the case of layer 14,with the previously cured resin layer in addition to the transparentfloor of the container.

In the example of FIG. 1, part 12 includes raft structure 16, which maycomprise one or more layers of material formed by stereolithographicprinter 100. As discussed above, the raft may increase adhesion betweenthe part and a build surface at least in part by providing a greatersurface area in contact between the part and build surface. As shown inFIG. 1, raft structure 16 contacts a greater area of build platform 4than part 12 would contact in the absence of the raft structure (i.e.,if part 12 were directly formed on build platform 4). A suitable raftstructure may extend across a build platform in any suitable way, andthe cross section of raft structure 16 shown in FIG. 1 may, for example,represent a cross section of a circular raft, rectangular raft or anyother suitable shape. In some use cases, such as those discussed above,however, part 12 may be difficult to remove from the build platform, atleast in part due to the increased adhesion between the part and thebuild platform.

FIG. 2 depicts a raft structure having removal pockets which, asdiscussed above, may provide for easier, safer and/or more efficientremoval of a part from a build platform. Raft structure 17 shown in FIG.2 may represent all or a portion of a raft structure formed on a buildplatform as part of initial layers of material formed during fabricationof a part. The body of a part that may be formed on the raft structure17 is not shown in FIG. 2 for purposes of clarity.

In the example of FIG. 2, the raft structure 17 includes removal pockets18 located along one edge of the structure in any manner ofconfigurations, e.g., evenly spaced. Such pockets may be designed toallow for a user to remove the raft structure from a build surface byexerting lifting and/or peeling forces. For example, the pockets 18 mayform void regions between the raft 17 and a build platform thatfacilitate insertion of a removal tool.

While, in the example of FIG. 2, pockets 18 are included at only oneedge of raft structure 17, in general pockets may be located at anynumber of locations along any edge or edges or the raft structure. Insome embodiments, the number and/or location of the pockets may dependat least in part on the geometry of the raft structure. In someembodiments, multiple pockets may be located continuously (e.g., evenlyspaced) around the perimeter of a raft structure, thus allowed forinsertion of a removal tool at various locations. A user may then choosea pocket most convenient for removal depending on the specificcircumstances (e.g., which pockets the user has access to).

According to some embodiments, one or more pockets are positioned duringdesign of a raft structure in the following way: the edge of a raftstructure without pockets may be defined as a two-dimensional, closedpolygon and a representation of the raft structure may be stored in asuitable computer readable medium. Then, the raft representation iscomputationally modified by combining a representation (e.g.,two-dimensional polygon cross-section) of a pocket structure with theraft representation. For example, the computational combination maycomprise using a polygon Boolean algorithm. Such algorithms may performBoolean operations on polygons to form unions, intersections,disjunctions, etc. of the polygons, e.g., by manipulating bitmaps orusing a sweep line algorithm.

In general, a removal pocket structure may be any structure having anopening at an exterior surface of a raft structure, which may be along abottom edge of the raft structure (e.g., so as to be adjacent to a buildsurface) or may be situated within a face of the raft structure (e.g.,so as to have material formed both above and below the pocketstructure). It may be advantageous for a pocket structure to have atapered shape such that the width of an opening decreases withincreasing distance from the exterior surface of the raft structure,though it may also have a shape that does not taper, or even widens withincreasing distance from the exterior surface of the raft structure. Apocket structure may be oriented parallel to a build surface, or may beoriented towards or away from a build surface such that a tool insertedinto the pocket may be naturally directed towards or away from the buildsurface. In some use cases, the orientation of the pocket structure maybe chosen to facilitate leverage provided to a removal tool by the shapeof the pocket. According to some embodiments, a raft structure mayinclude any combination of removal pocket structure variations describedherein.

According to some embodiments, following modification of arepresentation of a raft structure to include one or more removalpockets, one or more checks may be performed to determine whether themodification resulted in a valid addition of a pocket structure to theraft according to one or more criteria that may depend on the overalldesign of the system. In some embodiments, the following criteria may beevaluated: whether the proposed pocket structure is contained completelywithin the raft polygon representation; whether the proposed pocketstructure causes the raft structure to be divided, or split, intodistinct polygons; and/or whether any new polygon corners formed by theaddition of the pocket fall within a particular range of angles (e.g.,chosen so as to maintain the general contours of the raft structure). Ifany of the criteria being evaluated are found to be unsatisfactory, theraft structure may be further evaluated to determine alternate locationsfor the pocket structure(s) (e.g., by manual manipulation of thestructure and/or by automatic relocation of one or more pocketstructures).

FIGS. 3A-C depict an illustrative pocket structure in isometric, frontand side views, respectively, according to some embodiments. Raftstructure 300 may represent all or a portion of a raft structure formedon a build platform as part of initial layers of material formed duringfabrication of a part. The body of a part that may be formed on the raftstructure 300 is not shown in FIGS. 3A-C for purposes of clarity.

As shown in FIGS. 3A-C, a pocket structure 18 may introduce a void space22 underneath the raft structure 300. When raft structure 300 is formedon a build surface, the void space 22 will be located between the buildsurface and the pocket 18. In particular, the void space 22 in theexample of FIGS. 3A-C includes a raised portion 20 that is situatedabove the void space 22.

According to some embodiments, the raised portion 20 may be formed bydeflecting or raising a portion of the raft structure such that thepocket 18 is formed. As discussed above, a user may utilize a pocketstructure, such as pocket 18, to more easily remove raft structure 300from a build surface. For example, using a slotted screwdriver orsimilar prying tool, a user may insert the end of the tool into voidspace 22 formed by pocket 18, such that the tool extends below theraised surface portion 20 of the raft structure 300. According to someembodiments, the structure of pocket 18 may guide the user in apreferential placement of such a tool by having internal structure thatdirects motion of a tool toward the preferred placement. For example,the void space 22 and raised portion 20 of the pocket may be formed soas to decrease in height with increased depth from the edge of raft 300.

According to some embodiments, the slope of a pocket 18 may be chosen tocontrol the angle of approach of a removal tool or other device insertedinto the pocket to perform removal of the raft structure 300 from abuild surface. For example, a tool fully inserted into the pocket 18 maytend to rest against the build platform at the bottom and against thesloping structure 24 (shown in FIG. 3C) at the top. Accordingly, thetool may tend to form a similar angle against the build platform as theangle of the slope structure 24.

When a user removes raft 300 from a build surface, a tool can be pressedinto the pocket 18. The force of that application may contain multiplecomponents, including a “lifting” separating force normal to the buildplatform and/or a “shearing” separating force parallel to the buildplatform. The relative magnitude of these forces may be influenced andguided, at least in part, by the specified angle of the slope ofstructure 24 included in pocket 18. In some embodiments, pocketstructure 18 may be formed such that the void space 22 extendsapproximately 1.8 mm in height at its peak above the base level of theraft structure 300 along the perimeter of the raft structure, isapproximately 9 mm wide, and runs for 9 mm into the raft structure. Insome embodiments, the raised portion 20 of the raft extends forapproximately 2 mm above the peak of the void space.

FIG. 4 depicts an alternate pocket structure of a raft, according tosome embodiments. Raft structure 26 may represent all or a portion of araft structure formed on a build platform as part of initial layers ofmaterial formed during fabrication of a part. The body of a part thatmay be formed on the raft structure 26 is not shown in FIG. 4 forpurposes of clarity.

FIG. 4 illustrates an raft structure in which a void space may be formedwithout deflecting or raising a portion of a raft, by forming voidspaces 28. The shape of void spaces 28 may be particularly suitable forcertain removal tools. For example, a tool with a four-tined end may beparticularly appropriate to use to apply force into the pocketstructures shown in FIG. 4.

According to some embodiments, a raft structure such as raft structure26 shown in FIG. 4 and/or raft structure 300 shown in FIGS. 3A-C mayinclude void spaces that comprise one or more sacrificial structures. Asdiscussed above, such structures may be introduced into the void spacein order to strengthen and/or increase adhesions of the pocket to abuild surface, while also tending to collapse under the forces appliedto or through the pocket during removal of the raft structure from thebuild surface.

FIGS. 5A-B depict parts formed on a build structure including raftstructures having removal pockets, according to some embodiments.Additive fabrication device 500 shown in FIG. 5A includes a part 510formed on build platform 512, where part 510 includes a raft structure513 having removal pockets 514. As shown in the example of FIG. 5A, theremoval pockets extend upwards such that initial layers of the body ofpart 510 (shaped like a letter ‘H’ in the figure) are formed at the sameheight as regions of the removal pockets. In some use cases, a portionof the removal pocket may be formed in a layer that also includesportions of the body of the part (e.g., by forming material on top ofpreviously formed layers at a single height). In the example of FIG. 5A,raft structure 513 may a structure commensurate with, for example, raft300 shown in FIGS. 3A-C.

Additive fabrication device 550 shown in FIG. 5B includes a part 560formed on build platform 562, where part 560 includes a raft structure563 having removal pockets 564 (shown in hidden profile in the figure).In the example of FIG. 5B, raft structure 563 may a structurecommensurate with, for example, raft 26 shown in FIG. 4. As shown in theexample of FIG. 5B, the raft structure 563 has a completely flat uppersurface such that the raft structure may be completely formed prior toformation of any layers of the body of the part 560 (shaped like aletter ‘H’ in the figure).

FIG. 6 depicts a method of forming a raft structure including a removalpocket, according to some embodiments. Method 600 may be performed byany suitable additive fabrication device, including but not limited toadditive fabrication device 100 shown in FIG. 1.

In act 601, a raft structure is formed on a build platform. The raftstructure may include any number of layers of material, and may includeany number of removal pocket structures. The uppermost layers of theraft structure may include portions of the removal pocket(s), portionsor the raft structure other than the removal pocket(s), or both.

In act 602, additional material is formed in contact with the raftstructure. The additional material may comprise any number of layers ofmaterial, and may be the same or different material than was used toform the raft structure in act 601. The additional material may, forexample, represent an intended end result of the fabrication process.That is, subsequent to act 602, the raft structure may be removed fromthe additional material formed in act 602, substantially leaving onlythe additional material, which may represent the intended structurebeing produced. It may be appreciated that the raft formed in act 601and the additional material formed in act 602 may, but need not be,formed in distinct layers of material. For example, the uppermostportions of the raft structure (i.e., those formed lastly in act 601)may be formed in the same layer that one or more layers of theadditional material is formed in act 602. Such a case might arise wherethe raft structure has a lower height in a central portion and a higherheight around its perimeter such that the additional material may beformed on the central portion at the same time as the perimeter of theraft structure is formed.

In act 603, the raft structure and additional material are removed fromthe build platform. As discussed above, removal of a part having one ormore removal pockets in a raft structure may be performed by inserting asuitable tool into the removal pockets, or via any other suitable means.

FIGS. 7A-B depict front and isometric side views, respectively, of anillustrative grip structure attached to a body of a part having aspherical shape, according to some embodiments. As shown in FIG. 7A,part 700 includes a grip structure 2 and body 6 such that the grip 2 issuitable for use in supporting the body 6. In the example of FIGS. 7A-B,the intended end result of the fabrication process is a sphere, and thegrip 2 is formed attached to the body 6 which represents the intendedend result. Once post processing utilizing the grip 2 has beencompleted, the grip may be removed to leave body 6, the intended endresult of the fabrication process. As shown in FIGS. 7A-B, one exampleof a grip structure is a bent shape commonly known as a “hook.”

FIGS. 8A-B depict front and isometric side views, respectively, ofanother illustrative grip structure 2 formed for insertion into achannel shaped to receive such a grip structure within a supportingframe (e.g., a frame comprising parallel rails such that the top of grip2 sits on the rails while the central portion of the grip is between therails). Part 800 includes a grip structure 2 and body 6 such that thegrip 2 is suitable for use in supporting the body 6. Grip structure 2may be added to the body 6 such that an interface 4 is formed betweenthe part 6 and the grip structure 2 that is both adequate for thesupport of the part 6 during one or more post-processing steps andsufficiently easy to remove from the part 6 following and/or as part ofthe completion of such post-processing steps. Such an interface 4between the grip structure 2 and part 6 may be formed using one or moretechniques for the temporary attachment of removable support structures.Alternatively, grip structures and/or the interface may be formed usingvarious techniques known in the art for support structures from a secondmaterial that may be preferentially and/or selectively removed from apart formed of a first material.

FIG. 9 depicts an illustrative grip structure that includes features tofacilitate rotational movement around the grip structure, according tosome embodiments. Part 900 includes grip structure 2 formed in contactwith body 6. The grip structure includes notches 12 that may facilitaterotational movement of the part around the axis of the grip (e.g., theaxis that passes through the center of grip 2 and through the center ofthe spherical body 6).

FIG. 10 depicts an illustrative grip structure that includesinformation-carrier features and a registration mark, according to someembodiments. As depicted in FIG. 10, eight information-carrier features10 are located radially on a top surface of the grip structure 2. In theexample of FIG. 10, each information-carrier feature 10 may be in theform of a hole or deep indentation into the grip structure 2 and/or maybe in the form of a surface substantially planar with the top surface ofthe grip structure 2. According to the presentation, the configurationof such information-carrier features, including aspects such aslocation, size, and/or depth of holes, may be used to encodeinformation.

As one non-limiting example, each information-carrier feature may or maynot comprise a hole. Information-carrier features that do comprise holesmay be interpreted as the binary digit ‘1’, while information-carrierfeatures that do not comprise holes may be interpreted as the binarydigit ‘0.’ In this way, up to 256 possible values may be encoded usingeight such information-carrier features, which may utilize registrationmark 8 to indicate the beginning of such a sequence and ensure that suchdigits are read in the intended order.

Alternatively, or additionally, the depth, dimensions, and/or locationof an information-carrier feature may be altered in order to encode basen digits, wherein n represents the number of valid distinctconfigurations for a given information-carrier feature. Values encodedusing information features described above may be read by other systems,and/or end users, in any suitable way. In some embodiments, visualrecognition systems may be used to determine the configuration ofinformation-carrier features. In other embodiments, such as the exampledepicted in FIG. 10, information-carrier features may be physicallyprobed to determine their presence, size, location, and/or otherconfiguration. Values encoded using an information-carrier feature maythen be used by later post-processing systems to identify a given part,set process parameters based directly on the values encoded, and/oradjust existing process parameters as a function of the values encoded.

FIG. 11 illustrates an example of a suitable computing systemenvironment 1100 on which aspects of the invention may be implemented.For example, the computing system environment 1100 may be used toinstruct one or more force generators (e.g., actuators) to apply a forceto one or more regions of a container, to move a build platform, to movea wiper, or any combinations thereof. Such a computing environment mayrepresent a home computer, a tablet, a mobile device, a server and/orany another computing device.

The computing system environment 1100 is only one example of a suitablecomputing environment and is not intended to suggest any limitation asto the scope of use or functionality of the invention. Neither shouldthe computing environment 1100 be interpreted as having any dependencyor requirement relating to any one or combination of componentsillustrated in the exemplary operating environment 1100.

Aspects of the invention are operational with numerous other generalpurpose or special purpose computing system environments orconfigurations. Examples of well-known computing systems, environments,and/or configurations that may be suitable for use with the inventioninclude, but are not limited to, personal computers, server computers,hand-held or laptop devices, multiprocessor systems,microprocessor-based systems, set top boxes, programmable consumerelectronics, network PCs, minicomputers, mainframe computers,distributed computing environments that include any of the above systemsor devices, and the like.

The computing environment may execute computer-executable instructions,such as program modules. Generally, program modules include routines,programs, objects, components, data structures, etc. that performparticular tasks or implement particular abstract data types. Theinvention may also be practiced in distributed computing environmentswhere tasks are performed by remote processing devices that are linkedthrough a communications network. In a distributed computingenvironment, program modules may be located in both local and remotecomputer storage media including memory storage devices.

With reference to FIG. 11, an exemplary system for implementing aspectsof the invention includes a general purpose computing device in the formof a computer 1110. Components of computer 1110 may include, but are notlimited to, a processing unit 1120, a system memory 1130, and a systembus 1121 that couples various system components including the systemmemory to the processing unit 1120. The system bus 1121 may be any ofseveral types of bus structures including a memory bus or memorycontroller, a peripheral bus, and a local bus using any of a variety ofbus architectures. By way of example, and not limitation, sucharchitectures include Industry Standard Architecture (ISA) bus, MicroChannel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI) bus also known as Mezzanine bus.

Computer 1110 typically includes a variety of computer readable media.Computer readable media can be any available media that can be accessedby computer 1110 and includes both volatile and nonvolatile media,removable and non-removable media. By way of example, and notlimitation, computer readable media may comprise computer storage mediaand communication media. Computer storage media includes both volatileand nonvolatile, removable and non-removable media implemented in anymethod or technology for storage of information such as computerreadable instructions, data structures, program modules or other data.Computer storage media includes, but is not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium which can be used to store the desired informationand which can accessed by computer 1110. Communication media typicallyembodies computer readable instructions, data structures, programmodules or other data in a modulated data signal such as a carrier waveor other transport mechanism and includes any information deliverymedia. The term “modulated data signal” means a signal that has one ormore of its characteristics set or changed in such a manner as to encodeinformation in the signal. By way of example, and not limitation,communication media includes wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared and other wireless media. Combinations of the any of the aboveshould also be included within the scope of computer readable media.

The system memory 1130 includes computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) 1131and random access memory (RAM) 1132. A basic input/output system 1133(BIOS), containing the basic routines that help to transfer informationbetween elements within computer 1110, such as during start-up, istypically stored in ROM 1131. RAM 1132 typically contains data and/orprogram modules that are immediately accessible to and/or presentlybeing operated on by processing unit 1120. By way of example, and notlimitation, FIG. 11 illustrates operating system 1134, applicationprograms 1135, other program modules 1136, and program data 1137.

The computer 1110 may also include other removable/non-removable,volatile/nonvolatile computer storage media. By way of example only,FIG. 11 illustrates a hard disk drive 1141 that reads from or writes tonon-removable, nonvolatile magnetic media, a magnetic disk drive 1151that reads from or writes to a removable, nonvolatile magnetic disk1152, and an optical disk drive 1155 that reads from or writes to aremovable, nonvolatile optical disk 1156 such as a CD ROM or otheroptical media. Other removable/non-removable, volatile/nonvolatilecomputer storage media that can be used in the exemplary operatingenvironment include, but are not limited to, magnetic tape cassettes,flash memory cards, digital versatile disks, digital video tape, solidstate RAM, solid state ROM, and the like. The hard disk drive 1141 istypically connected to the system bus 1121 through an non-removablememory interface such as interface 1140, and magnetic disk drive 1151and optical disk drive 1155 are typically connected to the system bus1121 by a removable memory interface, such as interface 1150.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 11, provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 1110. In FIG. 11, for example, hard disk drive 1141 isillustrated as storing operating system 1144, application programs 1145,other program modules 1146, and program data 1147. Note that thesecomponents can either be the same as or different from operating system1134, application programs 1135, other program modules 1136, and programdata 1137. Operating system 1144, application programs 1145, otherprogram modules 1146, and program data 1147 are given different numbershere to illustrate that, at a minimum, they are different copies. A usermay enter commands and information into the computer 1110 through inputdevices such as a keyboard 1162 and pointing device 1161, commonlyreferred to as a mouse, trackball or touch pad. Other input devices (notshown) may include a microphone, joystick, game pad, satellite dish,scanner, or the like. These and other input devices are often connectedto the processing unit 1120 through a user input interface 1160 that iscoupled to the system bus, but may be connected by other interface andbus structures, such as a parallel port, game port or a universal serialbus (USB). A monitor 1191 or other type of display device is alsoconnected to the system bus 1121 via an interface, such as a videointerface 1190. In addition to the monitor, computers may also includeother peripheral output devices such as speakers 1197 and printer 1196,which may be connected through a output peripheral interface 1195.

The computer 1110 may operate in a networked environment using logicalconnections to one or more remote computers, such as a remote computer1180. The remote computer 1180 may be a personal computer, a server, arouter, a network PC, a peer device or other common network node, andtypically includes many or all of the elements described above relativeto the computer 1110, although only a memory storage device 1181 hasbeen illustrated in FIG. 11. The logical connections depicted in FIG. 11include a local area network (LAN) 1171 and a wide area network (WAN)1173, but may also include other networks. Such networking environmentsare commonplace in offices, enterprise-wide computer networks, intranetsand the Internet.

When used in a LAN networking environment, the computer 1110 isconnected to the LAN 1171 through a network interface or adapter 1170.When used in a WAN networking environment, the computer 1110 typicallyincludes a modem 1172 or other means for establishing communicationsover the WAN 1173, such as the Internet. The modem 1172, which may beinternal or external, may be connected to the system bus 1121 via theuser input interface 1160, or other appropriate mechanism. In anetworked environment, program modules depicted relative to the computer1110, or portions thereof, may be stored in the remote memory storagedevice. By way of example, and not limitation, FIG. 11 illustratesremote application programs 1185 as residing on memory device 1181. Itwill be appreciated that the network connections shown are exemplary andother means of establishing a communications link between the computersmay be used.

The various methods or processes outlined herein may be implemented inany suitable hardware. Additionally, the various methods or processesoutlined herein may be implemented in a combination of hardware and ofsoftware executable on one or more processors that employ any one of avariety of operating systems or platforms. For example, the variousmethods or processes may utilize software to instruct a processor toactivate one or more actuators to perform motions such as thosedescribed herein, such as motion of one or more regions of a containerand/or of a build platform. Examples of such approaches are describedabove. However, any suitable combination of hardware and software may beemployed to realize any of the embodiments discussed herein.

In this respect, various inventive concepts may be embodied as at leastone non-transitory computer readable storage medium (e.g., a computermemory, one or more floppy discs, compact discs, optical discs, magnetictapes, flash memories, circuit configurations in Field Programmable GateArrays or other semiconductor devices, etc.) encoded with one or moreprograms that, when executed on one or more computers or otherprocessors, implement the various embodiments of the present invention.The non-transitory computer-readable medium or media may betransportable, such that the program or programs stored thereon may beloaded onto any computer resource to implement various aspects of thepresent invention as discussed above.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects of embodiments as discussedabove. Additionally, it should be appreciated that according to oneaspect, one or more computer programs that when executed perform methodsof the present invention need not reside on a single computer orprocessor, but may be distributed in a modular fashion among differentcomputers or processors to implement various aspects of the presentinvention.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically, the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Various inventive concepts may be embodied as one or more methods, ofwhich examples have been provided. For example, systems and methods foradditive fabrication that form structures to assist in post-processingof an associated fabricated part have been provided herein. The actsperformed as part of any method described herein may be ordered in anysuitable way. Accordingly, embodiments may be constructed in which actsare performed in an order different than illustrated, which may includeperforming some acts simultaneously, even though these acts may havebeen shown as sequential acts in illustrative embodiments.

While auxiliary structures having raft and grip structures are describedherein, other auxiliary structures may be used in addition oralternatively to these structures. For example, auxiliary structures mayinclude tabs, handles or other structures to aid in removal of a partfrom a build surface. In addition, any number and type of auxiliarystructures may be formed in a part using techniques described herein, asthe invention is not limited in this aspect. For example, a raftstructure and one or more grips may be formed in a part. Further, theauxiliary structures formed may be of any size, thickness, layerdensity, material, etc. which may be different from other regions of thesame part. For example, multi-material additive fabrication devices mayproduce auxiliary structures having different densities than the body ofthe part.

In some use cases, it may be advantageous to modify post processingsteps for a given part based on build style, material parameters, orother aspects that may be particular to the part or particular additivemanufacturing process used to form said part. Further, it may beparticularly advantageous for such modifications to be handled in atleast a semi-automated fashion, e.g., without substantial userinvolvement. As such, automated processes used in a finishing processmay benefit from exchanging information from systems and apparatusesused in the printing process to systems and apparatuses used in thefinishing process. Such information may be exchanged in varioustechniques, such as networked communications, digital storage, and/ormanual entry. One aspect of the present invention allows for a widevariety of information associated with a part to be exchanged betweenfabrication and post processing systems by altering portions of thegeometry added to the part as grip structures, or structures potentiallyadded for the purpose of information exchange only.

The methods and techniques described herein may be implemented in anysuitably programmed general-purpose computer, a special-purpose computerdevice (e.g., a digital signal processor, programmable gate array,application-specific integrated circuit, etc.), or generally anysuitable combination of hardware and/or software. The computer may beintegrated into the additive fabrication device or an associated printercontroller, or provided separately in communication with the printerand/or controller. For example, in some embodiments, a computerincluding at least a processor and system memory (e.g., RAM), andtypically also one or more non-volatile storage devices and media (suchas, e.g., a hard drive, optical storage medium, or USB key), userinterface devices (such as, e.g., a display screen, keyboard, andmouse), and a network interface, may store, in the memory,process-executable instructions implementing design of any suitableauxiliary structure (including, e.g., instructions for computationallymodifying a representation of a raft structure and/or validating amodified design based on certain criteria) and/or directing an additivefabrication device to fabricate a designed part including one or moreauxiliary structures.

Programming instructions that, when executed, perform any method ortechnique described herein may be in any suitable language (includinghigh-level languages such as C++, C, Fortran, Python, BASIC, Pascal,etc. or assembly or other low-level languages), and may be grouped andorganized into various modules. The computer may be connected, via awired or wireless network (e.g., Ethernet, WLAN, or the Internet) to theadditive fabrication device (and/or its controller), and the device maybe operated based on a computational representation (e.g., datadescriptive) of a part including one or more auxiliary structures.

Data describing a three-dimensional object suitable for fabricationusing an additive fabrication device may be described using any suitableformat, including any data format that defines a three-dimensionalgeometry (e.g., by defining positions of vertices, normals and/orfaces). A non-limiting list of suitable formats for an input shape mayinclude STereoLithography (STL), Wavefront OBJ, Additive ManufacturingFile Format (AMF), ObjDF, Stratasys SLC, Zmodeler Z3D, Lightwave LWO,Autodesk Maya and/or 3D Studio Max, etc.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein, unless clearlyindicated to the contrary, should be understood to mean “at least one.”

As used herein, the phrase “at least one,” in reference to a list of oneor more elements, should be understood to mean at least one elementselected from any one or more of the elements in the list of elements,but not necessarily including at least one of each and every elementspecifically listed within the list of elements and not excluding anycombinations of elements in the list of elements. This definition alsoallows that elements may optionally be present other than the elementsspecifically identified within the list of elements to which the phrase“at least one” refers, whether related or unrelated to those elementsspecifically identified.

The phrase “and/or,” as used herein, should be understood to mean“either or both” of the elements so conjoined, i.e., elements that areconjunctively present in some cases and disjunctively present in othercases. Multiple elements listed with “and/or” should be construed in thesame fashion, i.e., “one or more” of the elements so conjoined. Otherelements may optionally be present other than the elements specificallyidentified by the “and/or” clause, whether related or unrelated to thoseelements specifically identified. Thus, as a non-limiting example, areference to “A and/or B”, when used in conjunction with open-endedlanguage such as “comprising” can refer, in one embodiment, to A only(optionally including elements other than B); in another embodiment, toB only (optionally including elements other than A); in yet anotherembodiment, to both A and B (optionally including other elements); etc.

As used herein, “or” should be understood to have the same meaning as“and/or” as defined above. For example, when separating items in a list,“or” or “and/or” shall be interpreted as being inclusive, i.e., theinclusion of at least one, but also including more than one, of a numberor list of elements, and, optionally, additional unlisted items. Onlyterms clearly indicated to the contrary, such as “only one of” or“exactly one of,” will refer to the inclusion of exactly one element ofa number or list of elements. In general, the term “or” as used hereinshall only be interpreted as indicating exclusive alternatives (i.e.“one or the other but not both”) when preceded by terms of exclusivity,such as “either,” “one of,” “only one of,” or “exactly one of.”

The phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” “having,” “containing”, “involving”, andvariations thereof, is meant to encompass the items listed thereafterand additional items.

Having described several embodiments of the invention in detail, variousmodifications and improvements will readily occur to those skilled inthe art.

For example, techniques of separating a portion of a part formed throughadditive fabrication from a surface were described. These techniques maybe applied in other contexts. Any device or process that fabricatesobjects may utilize techniques for including auxiliary structures asdescribed herein. For example, a part manufacturing via reductivemanufacturing may make use of a grip structure as described herein. Suchmodifications and improvements are intended to be within the spirit andscope of the invention. Accordingly, the foregoing description is by wayof example only, and is not intended as limiting.

What is claimed is:
 1. (canceled)
 2. At least one non-transitorycomputer readable medium comprising instructions that, when executed byat least one processor, perform a method of configuring an additivefabrication device to fabricate a part, the method comprising: obtaininga first three-dimensional model representing a part to be fabricated bythe additive fabrication device; generating, using the at least oneprocessor, a second three-dimensional model by incorporating at leastpart of a three-dimensional model of an auxiliary structure into thethree-dimensional model representing the part to be fabricated, whereinthe auxiliary structure comprises one or more shapes that conveyidentifying information to a user that identifies the part to befabricated as being distinct from other parts; and generating, using theat least one processor, instructions that, when executed by the additivefabrication device, cause the additive fabrication device to fabricatethe part and the auxiliary structure as a first object according to thesecond three-dimensional model.
 3. The at least one non-transitorycomputer readable medium of claim 2, wherein incorporating the at leastpart of the three-dimensional model of the auxiliary structure into thethree-dimensional model representing the part to be fabricated comprisesinserting the three-dimensional model of the auxiliary structure intothe three-dimensional model representing the part to be fabricated. 4.The at least one non-transitory computer readable medium of claim 2,wherein incorporating the at least part of the three-dimensional modelof the auxiliary structure into the three-dimensional model representingthe part to be fabricated comprises a Boolean union operation betweenthe three-dimensional model representing the part to be fabricated andthe three-dimensional model of the auxiliary structure.
 5. The at leastone non-transitory computer readable medium of claim 2, wherein theauxiliary structure comprises a grip structure.
 6. The at least onenon-transitory computer readable medium of claim 2, wherein the one ormore shapes of the auxiliary structure convey identifying informationvia the location and/or size of the shapes.
 7. The at least onenon-transitory computer readable medium of claim 2, wherein the part isa first part, wherein the generated instructions also, when executed bythe additive fabrication device, cause the additive fabrication deviceto fabricate a second part together with the first part and theauxiliary structure, the second part having a different shape than thefirst part, and wherein the one or more shapes of the auxiliarystructure indicate that the first object comprises the first part andnot the second part.